The purpose of this research is to examine the process of membrane- initiated biologic calcification by identifying and characterizing structural-functional relationships which facilitate the mineralization process. Calcification of Bacterionema matrichotii, an oral actinomycete which forms intracellular apatite deposits, will be used as a model. The proposed experiments will: 1. identify membrane characteristics associated with particular mineral phases in the process of apatite formation by chemical, biochemical and ultrastructural analyses of density gradient fractions of B. matruchotii at different stages of calcification; 2. identify and characterize specific structural-functional relationships which facilitate calcification by biochemical analysis of proteolipid-mineral complexes and associated membrane phospholipids and by histochemical localization of enzymes and antibody tagged proteolipid in calcifying membrane domains; and, 3. examine cellular regulation by investigating changes in the structural-functional relationships with time, cell Ca/Mg and calcification status. Calcifying, non-calcifying and non-calcifiable (Actinomyces naeslundii) cells will be compared. Methodology will be developed for application to normal and pathologic vertebrate calcification.